Why the Controller could resist a First Sea Lord

The Controller of the Navy chaired the Navy Board and controlled dockyards, infrastructure, and procurement. Although the First Sea Lord was the senior professional officer, the Controller served at the pleasure of the civilian First Lord of the Admiralty. The same inherited arrangement applied when the Third Sea Lord also held the Controller's office. Constitutional convention and repeated precedent prevented First Sea Lords from countermanding orders within the Controller's proper remit. First Sea Lords who tested the boundary lost, making inherited office custom a practical source of institutional power.